1. Field of the Invention
The present invention relate to a liquid crystal display (LCD) apparatus, and more particularly, to the alignment of a flexible printed board with a glass substrate.
2. Description of the Related Art
Generally, an LCD apparatus is constructed by a glass substrate, an LCD panel mounted on the glass substrate, and a flexible printed board adhered to the glass substrate. The flexible printed board drives the LCD panel. Therefore, the flexible printed board has leads electrically connected to the LCD panel and an insulating layer partly covering the leads.
In a first prior art LCD apparatus, connection terminals are formed along edges of the glass substrate. The leads of the flexible printed board are connected to the connection terminals by a thermocompression bonding process using a thermosetting conductive adhesive agent. When connecting the leads of the flexible printed board to the connection terminals of the glass substrate, the conductive adhesive agent is heated while the flexible printed board is lowered under pressure until they are connected with each other. This will be explained later in detail.
In the above-described first prior art LCD apparatus, however, while the leads and the insulating layer are located respectively at different levels on the flexible printed board, the connection terminals of the glass substrate are on the same plane as the compression bonding surface at the time of the thermocompression bonding process, so that the insulating layer is inevitably located off the edge of the glass substrate. Therefore, the leads of the flexible printed board are left uncovered and exposed to the atmosphere, resulting in conductive contaminant adhered to the exposed leads, which may by turn give rise to a short-circuiting therein.
In a second prior art LCD apparatus (see JP-A-5-72545 & JP-A-8-138774), an about 0.3 to 1.0 mm width beveled section is formed along the edge of the glass substrate. As a result, when the conductive adhesive agent is forced off the edge of the glass substrate by the thermocompression bonding process, squeezed adhesives is received in the beveled section. Therefore, the leads of the flexible printed board are completely covered by the adhesive agent, thus avoiding a short-circuit between the leads of the flexible printed board. This also will be explained later in detail.
In the above-described second prior art LCD apparatus, however, since it is difficult to closely control the flow of the conductive adhesive agent, and also the location of the edge of the insulating layer fluctuates, the exposed leads of the flexible printed board may not be covered satisfactorily. In addition, since the part of the conductive adhesive agent that is forced off will simply remain by chance on the beveled section of the glass substrate, when subjected to stress due to external force or made to become brittle for some reason or other, the part of the conductive adhesive agent can easily come off the beveled section of the glass substrate, to thereby affect the operation of the LCD apparatus as foreign objects blocking the back light.